U.S. brand Victoria's Secret will open its first store, and companies including Italy's ultra-luxury La Perla and Germany's Triumph are adding stores and moving beyond China's mega-cities to tap a lingerie market that has more than doubled in five years to $18 billion, according to Mintel Group.

Chinese consumer tastes are maturing, women are more confident about buying for themselves and President Xi Jinping's drive against conspicuous consumption is likely diverting spending from flashy branded bags and accessories to sports and ath-leisure wear and the more discreet lingerie.

"Luxury is ... not about buying to show off, it's about buying items that make you feel good," says Chiara Scaglia, La Perla's Asia chief.

China's women's underwear market is expected to have a retail value of $25 billion by next year - double that of the United States - and will grow to $33 billion by 2020, according to Euromonitor.

Chinese firms such as Beijing Aimer, Maniform and Ordifen are also chasing that money, targeting higher-end customers and raising their quality.

"That means foreign brands will have to out-compete local brands not just on quality, but also innovation," said Matthew Crabbe, director at Mintel.

For now, the market is highly fragmented, with none of the leading firms having more than around a 3 percent share. International brands see China as a priority to help bolster overall sales given a fairly bleak global outlook.

La Perla, which sells bras priced around 2,000 yuan ($300), has eight stores in China and plans additional outlets in Chengdu and Chongqing within the year. It also aims to open a men's store in Beijing.

"The perception of the lingerie sector has changed," Scaglia told Reuters. "At the beginning many people we spoke to were confused as to why anybody should spend over $1,000 on panties for something nobody sees."

EXPANDING FOOTPRINT

Victoria's Secret will open a 20,000 square foot (1,860 square meter) flagship store in Shanghai this year, taking over a prime downtown location that used to house a Louis Vuitton store. "I think it will announce our arrival in China in a very significant way, and should be the beginning of an enormous business for us," said Martin Waters, L Brands International President.

Triumph, which already has 1,000 China stores, plans to open in five new cities this year and up to 11 cities next year.

Cosmo Lady 2298.HK, a Chinese firm that has focused on the mass market, selling bras from 50 yuan ($7.50), last year bought Ordifen to increase its presence in the luxury market.

"We would like to gradually step into the high-end market," said Peter Lam, Cosmo Lady's assistant chief financial officer.

Gao Qiannan, a 22-year-old Shandong student who says she spends upwards of 1,500 yuan a year on lingerie, doesn't think there's a big difference between Chinese and foreign brands.

"If I can buy a domestic brand, I will, but if I particularly like the international brand's style, I'll get that," she said.

The international brands say they don't offer products specifically for the Chinese market, though La Perla notes that some colors - red and baby pink - sell far better in Asia than in Europe or the United States. The Italian brand has also used Chinese supermodel Liu Wen in its campaigns.

Japanese and South Korean brands are also growing in popularity in China.

Yin Huijuan, 23, who spends 800 yuan ($120) on lingerie every three months, said she prefers Japanese brands such as Wacoal and Narue. "I feel foreign brands' style is more detailed and diversified, these are areas where domestic brands fall short," she said.

CONSUMER CAUTION, ONLINE COMPETITION

Even in the lingerie market, though, there are bumps.

Cosmo Lady, which has 8,600 outlets including Ordifen's 550 China stores, saw robust growth in its mass market sales last year, but has warned about its profits for the first half of this year, citing China's slowing economic growth, consumer caution and competing online sales.

Hong Kong-listed Embry Holdings (1388.HK), which owns the Embry Form lingerie brand, said its group retail sales slipped by nearly a fifth in April-June on tougher competition and the economy.

Despite those bumps, the lingerie sector retains a strong appeal, said Eugene Mak, an analyst at China Merchant Securities in Hong Kong, and firms like Cosmo Lady are still outperforming other apparel retailers.

He predicts the market will hit a consolidation phase at some time. "It's a very young market, but in the near-term it's going to be messy," he said.